Redundant VDT Position Sensor Eliminates Potentiometer Wear
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Solution Overview
Problem
Potentiometers used in aircraft pilot control units suffer from wear and reduced endurance due to contact between the wiper and resistive track, leading to decreased accuracy, increased noise, and potential loss of contact.
Innovation Solution
A contactless position sensing system utilizing a variable differential transformer (VDT) with AC/DC conversion to provide two independent DC output signals, which indicate the position of the input shaft, and includes features like RMS to DC conversion, gain and offset calibration, and electromagnetic interference protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If potentiometers are used for position sensing, then the electrical interface is simple and multiple outputs can be provided in a small volume, but wear and endurance are reduced due to contact between the wiper and resistive track
Solution Approach 1:
The patent replaces the mechanical contact-based potentiometer system with a contactless VDT system. The VDT uses electromagnetic coupling between primary and secondary coils to sense position without physical contact, eliminating wear between wiper and resistive track while maintaining reliability and endurance.
Solution Approach 2:
The patent introduces AC/DC conversion circuitry as an intermediary between the VDT's AC output and the DC-based aircraft systems. This conversion layer enables compatibility with existing DC interfaces while allowing the VDT to operate with its superior contactless AC output signal.
2Measurement precision
If potentiometers are used for position sensing, then multiple outputs can be provided in a small volume, but wear leads to decreased accuracy and increased noise
Solution Approach 1:
The patent replaces the mechanical contact-based potentiometer system with a contactless VDT system. The VDT uses electromagnetic coupling between primary and secondary coils to sense position without physical contact, eliminating wear between wiper and resistive track while maintaining reliability and endurance.
3Reliability
If a contactless sensing system like VDT is used, then wear is eliminated and endurance is improved, but the electrical interface complexity increases
Solution Approach 1:
The patent introduces AC/DC conversion circuitry as an intermediary between the VDT's AC output and the DC-based aircraft systems. This conversion layer enables compatibility with existing DC interfaces while allowing the VDT to operate with its superior contactless AC output signal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system offers improved endurance and reliability by eliminating track wear, providing accurate and stable position sensing with a compact, cost-effective solution that can be easily integrated into existing systems.
Implementation Method 1
a primary coil configured to provide a magnetic field, and a first and second secondary coils electromagnetically coupled to the primary coil. Movement of said input shaft varies a voltage induced by each of the secondary coils
Implementation Method 2
a first AC/DC converting means that is configured to convert said first AC output signal to a first DC output signal; and a second AC/DC converting means that is configured to convert said second AC output signal to a second DC signal
Data Source
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AI summary
A position sensing system (302) for sensing a position of an input shaft of a variable differential transformer (VDT), comprising said VDT (310), which comprises first and second AC signal output means that are configured to output a first AC output signal and a second AC output signal respectively. The sensing system (302) further comprises AC/DC converting means (333) configured to convert said first AC output signal to a first DC output signal and an AC/DC converting means (343) configured to convert said second AC output signal to a second DC signal. The first and second DC output signals each indicate an individual position of said input shaft.